It means that you may not have obeyed all the writing rules perfectly in every element in your manuscript, but the story itself is so great that an editor doesn’t want to put it down. And if they are having trouble putting it down, so will readers. Editors will be willing to work with you on the mechanics of writing in order to get that “great story” to the level it should be and published.
This doesn’t mean that the manuscript can be in any condition and sloppy. All the basics of good writing will have to be present—just not perfect.
I have seven completed manuscripts. Of those, I have a few favorites in spite of the fact that I’m the author of all of them. Something about those stories grip me, even as a reader. My writing is the same in each one. So what is it that makes those stories stand out among the others, as better than the standard of all that I’ve written? It’s the story itself, the characters and the overall plot that a reader can identify with and cheer them on. It isn’t necessarily the writing. A person could recite and tell each story, and those stories would still be more compelling to the ear.
These are also the stories that have finaled in contests and received requests from editors to submit the complete manuscripts. When a story is getting noticed, make sure you work on the writing elements and obey as many writing rules as possible. Eventually, it will be noticed by the right person to get it published.
If you’ve been shopping a manuscript around from place to place and no one seems to be interested, put it down and concentrate on a new, fresh story. It may not be your writing that is the problem. It may be your story. Because when you have a great story, it always trumps the writing. And people notice—especially editors.